Dual speed clutches with brake

ABSTRACT

A DEVICE FOR DRIVING AND STOPPING A MACHINE, MORE PARTICULARLY A SEWING MACHINE. BETWEEN AND ELECTRIC DRIVING MOTOR AND AN OUTPUT PULLEY OR THE LIKE CONNECTED TO THE MACHINE, THERE IS PROVIDED A SPEED-REDUCING TRAIN AND AN ELECTROMAGNETIC-CLUTCHING AND -BRAKING DEVICE. THE LATTER COMPRISES TWO COAXIAL COILS, ONE OF WHICH CONTROLS THE CLUTCHING BY CAUSING, UPON EXICITATION, THE MOVEMENT OF AN ASSEMBLY INTEGRAL WITH A CLUTCH-COUPLING MEMBER AND THE OTHER ONE OF WHICH CONTROL THE BRAKING BY APPLICATION OF A FRACTION PACKING HOUSED IN A SUPPORT OF SAID ELECTROMAGNETIC DEVICE AGAINST A PLATE INTEGRAL WITH THE MOVEABLE ASSEMBLY.

United States Patent Inventors DUAL SPEED CLUTCHES WITH BRAKE 9 Claims,11 Drawing Figs.

U.S. Cl 192/18, 188/161, 192/9, 192/48.2, 112/219, 317/157, 192/142lnt.Cl Fl6d 67/06 Field of Search ..192/9, 12.2, 18.2

Primary Examiner- Benjamin W. Wyche Attorney-limestF. Marmorek ABSTRACT:A device for driving and stopping a machine, more particularly a sewingmachine. Between an electric driving motor and an output pulley or thelike connected to the machine, there is provided a speed-reducing trainand an electromagnetic-clutching and -braking device. The lattercomprises two coaxial coils, one of which controls the clutching bycausing, upon excitation, the movement of an assembly integral with aclutch-coupling member and the other one of which controls the brakingby application of a friction packing housed in a support of saidelectromagnetic device against a plate integral with the movableassembly.

PATENIEU JUN28 I971.

3587.797 sum 1 0r 6 F E. mm on mm K2 2 a PATENTEU JUN28 19m SHEET 2 OF 6PATENTED JUN28 197i SHEET U, [1F 6 v/zi 227 n 1 WW DUAL SPEED CLUTCIIESWITII BRAKE FIELD OF THE INVENTION The invention relates to a drivingand stopping device of a machine, more especially of a sewing machinecomprising, between an electric driving motor and an output pulley orthe like connected to the machine, a speed-reducing train and anelectromagnetic-clutching and braking device.

SUMMARY OF THE INVENTION It is an object of the invention to supply sucha device which is of simple construction, of reliable function andpractically devoid of breakdowns.

According to the invention, this object is achieved in that theelectromagnetic device comprises, in a sliding support, two coaxialcoils, one of which controls the uncoupling by sliding displacement of amovable assembly integral with a coupling member and the other of whichbrings about the braking by application of a friction packing, housed insaid support, against a plate integral with said assembly.

In one embodiment, the device comprises means for ensuring the stoppageof the machine in a predetermined position.

Advantageously, these means supply a current impulse at each rotation ofa member forming part of the machine, said impulse having a width thewider as the member rotates more slowly and being used for the controlof an electronic threshold member controlling the putting into action ofthe braking. When used on a sewing machine, the device according to theinvention permits driving at all the speed conditions desired from amaximum speed down to a minimum speed and, inversely, also permits thestoppage of the machine to be obtained in a very short time, the needleof the sewing machine being for the effective stoppage always in thesame position, for example the lower position.

The device according to the invention also permits, from thelast-mentioned position, the machine to be conducted automatically intoanother predetermined position, for example that which corresponds tothe upper position of the needle.

The device in accordance with the invention therefore permits, inconjunction with a sewing machine, the work of sewing to be facilitatedand speeded up.

The invention will be understood from the description which follows,given by way of example, and with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial view inlongitudinal section and with parts broken away of a device inaccordance with the invention, for a first embodiment;

FIG. 2 is a partial view in longitudinal section'and with parts brokenaway, but for another part of the device;

FIG. 3 is a view, partly in longitudinal section, partly in elevationwith parts broken away, on a smaller scale and for a modification;

FIG. 4 is a longitudinal sectional view of a device provided for theautomatic performance of the operation of a machine provided with adriving device in accordance with one or other of the precedingembodiments;

FIG.-5 is a sectional view along line 5-5 in FIG. 4;

FIG. 6 is an electrical diagram;

FIGS. 7 to 11 are diagrams.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is first made toFIGS. 1 and 2. The device comprises an electric motor 10, which can beof the conventional type having a single speed, for example of the orderof 3,000 r.p.m., as usual. Keyed on the shaft 11 of the electric motor,near the outlet of the case or housing 12 of the motor proper, is awheel 13 of small diameter, having a toothed rim 14, with whichcooperates a notched belt 15 which also cooperates with a wheel 16 oflarge diameter, having a toothed rim 17. The wheel 16 is integral, byits hub 18, with an intermediate shaft 19, which rests, by means of acollar 20, in a bearing 21 forming part of a first case body 22 of thedevice. Keyed on the intermediate shaft 19 there is, in addition, asecond wheel 23, of small diameter, having a toothed rim, with whichcooperates a notched belt 25 which also cooperates with the toothed rim26 of a wheel 27 of large diameter. The wheel 27 rests, for rotation, bya ball bearing 28, on a boss 29 forming part of the second case body 30.

Keyed on the shaft 11, by its hub 31, is a flywheel 32, which thusrotates at the speed of the electric motor. The shaft 11 is supported byan annular boss 33 of the case 22 with insertion of a ball bearing 34. Acollar 35 is interposed between said bearing and the wheel 13 and awasher 36 ensures the holding of the flywheel 32. The circlips" 37 and38 locate the ball bearing 34.

In the boss 29 is slidingly mounted, with interposition of a sleeve fromwhich there projects a guiding finger 51, a socket 52 having a groove 53cooperating with the finger 51. The socket 52 forms part of a slidingassembly 54 which comprises a rotary shaft 55 whose axis is aligned withthat of the shaft 11 of the electric motor, the shaft 55 being mountedfor rotation in the socket 52 with interposition of a ball bearing 56.The bearing 56 is framed by a thrust part 57 on the one hand and ashoulder 58 of the shaft 55 on the other hand. Fixed by means of screws60 on a shoulder 59 of larger diameter is a plate 61 which carries, onits opposite faces 62 and 63, friction packing 64 and 65 respectively.

The thrust part 57 has, besides its front face 66 cooperating with theball bearing 56, a flange 67 with which is integral an annular plate 68.A cheek 69 integral with the case body 30 carries by their feet pins 70,for example three in number, which are housed in bores 71 of a coilsupport or yoke 72. The latter is of a general disc shape, and has anexternal annular housing 73 and an internal annular housing 74 whichrespectively receive a first annular coil 75 and a second annular coil76. The external front face 77 of the yoke 72 is immediately facing theinternal front face 79 of the plate 68. Springs 72a, housed in bores ofthe yoke 72 and resting on the other hand on the cheek 69, pull the coilsupport 72 away from said check.

In the central bore 79 of the body 72 passes freely a tubular strut 80surrounding the shaft 55 and integral with the latter. Said strut abutsat its external end against the thrust part 57 and at its internal endagainst a ball bearing 81 interposed between the shaft 55 and a sleeve82. The latter has a port 83 in which there is engaged a swivel 84 whichforms the end of a lever 85 mounted for rotation about a spindle 86carried by the frame of the machine; the lever 85 has a branch 87terminating in the swivel 84 and which is continued by a branch 88substantially at a right angle, the end of which has a hole 89 where canengage a chain or the like solicited by a pedal, which, when one presseson it, exerts a pull in the direction marked by thearrow f. The arm 88comprises a tubular body 103' inside which there is housed an arm 105mounted for articulation about a spindle 106 which is carried by thelever, in its connecting zone between the branches 87 and 88. It is onsaid arm 105 that there is provided the hole 89 of the chain. On arm105, there is exerted, by means ofa seat 106 which it possesses, theaction of a spring 107, resting on the other hand on the interior faceof the body 103' and which thus tends to urge the control button 108 ofa microswitch 109 carried by the arm 105 against a fixed stop 110 ofadjustable position, carried by body 103'.

An annular cap 90 is integral with the sleeve 82 through screws 78 andits internal rim 91 butts against the ball bearing 81; its external rim92 can slide against a rim 93 of the cover 94 of the case of the devicecomprising a tubular projection 94' in which the sleeve 82 is mountedslidingly. The cover 94 has bores 95 in which are housed spiral springs96 which are braced on the other hand against the cap 90. One or morescrews 97, mounted in tapped holes of the cover 94, can cooperate withthe internal face 98 of the body 72.

Means are provided to feed the coil 75 and the coil 76 with electricalcurrent.

The operation is as follows:

In the condition of rest, the sliding assembly 54 is in its right-handend position, as shown in FIG. 1 and FIG. 2, under the action of thesprings 96. In this position, the plate 61 is in its position for whichthe packing 65 can cooperate with the wheel 27. When, through bearing onthe pedal, one exerts a slight pull on the arm 105, this latter pivotsabout the spindle 106 against the action of the spring 107; theprojection of the button 108 of the microswitch 109 interrupts thecurrent in the coil 76 so that the packing 102, carried by a packingcarrier 103, is moved away from the annular plate 68, ensuring thedebraking in rotation of the sliding assembly 54. The packing 65 of theplate 61 cooperates with the wheel 27, driven by the electric motor at acomparatively low speed, by virtue of the double reduction introduced onthe one hand by the pair of wheels 13- 16 and on the other hand by thepair of wheels 23- -27. The machine is driven at a low speed, by meansof the pulley 100 keyed on the shaft 55 with which the plate 61 isintegral.

When the pull exerted on the arm 105 becomes stronger, it is the wholeof the lever 85 which pivots about the axis 86; the sliding assembly 54,comprising the sleeve 82, the cap 90, the ball bearing 81, the tubularstrut 80, the stop piece 57, the ball bearing 56, the socket 52, theplate 61 and the shaft 55, is driven from right to left by the action ofthe swivel 84, exerting on the sleeve 82 against the action of thesprings 96, the packing 65 draws away from the wheel 27 driven at a lowspeed and the packing 64 cooperates with the internal front face 101 ofthe flywheel 32 the latter, keyed directly on the shaft 11 of theelectric motor, rotates at the high speed. Fol lowing the more or lessdeep sinking of the pedal, the pressure exerted by the packing 64against the front face 101 is more or less great for a highly sunkenposition of the pedal, the pressure is sufficient for the plate 61 torotate at the speed of the flywheel 32; the pulley 100 is then driven atthe maximum high speed; if the pedal is less sunken, there is produced asliding between the packing 64 and the face 101 of the flywheel 32; thespeed of the pulley 100, as well as that of the machine, diminish. Onecan thus regulate in a progressive manner the speed of the machinebetween the maximum high speed and the low speed.

To stop the machine, the operator ceases to exert pressure on the pedal,so that the machine is driven at a low speed, and the braking drive istriggered by feeding the coils 75 and 76. Through the feed of coil 75,the bobbin support 72, initially in contact by its face 98 with the endsof the screws 97, under the action of the springs 72a, is attractedmagnetically by the cheek 69, so that there is produced, by cooperationof the said support 72 with the plate 68, a sliding of the slidingassembly 54 from the right towards the left (in FIG. 1), which draws thepacking 65 away from the wheel 27 and thus ensures the uncoupling of theshaft 55 and of the members rotating with it with regard to the drivingdevice. The abutment of the coil support 72 against the cheek 69interrupts the slide of the assembly 54 before the packing 64 of theplate 61 can cooperate with the flywheel 32.

The feed of the coil 76 creates a magnetic field which ensures anapplication under strong pressure of a packing 102, carried by a packingcarrier 103 closing the annular housing 74 of the nonrotary coil support72 in which is housed the winding 76, against the plate 68 of therotating assembly 54, so that there results a strong braking of thelatter, therefore of the pulley 100 and of the members connected to thesame.

The application force of the packing 102 against the plate 68, whichgives rise to the braking, has a predetermined value resulting both fromthe characteristics of the coil 76 and from those of the springs 96 andthe braking action is exerted on a rotating assembly disconnected fromthe motor, so that when it rotates at a predetermined speed, thestoppage is obtained in a well-determined position in relation to thatin which the stopping process of the machine has been initiated.

When the machine is stopped, if one interrupts the feed of the coils 75and 76, one can resume the normal operation of the machine, either at alow speed, or at a high speed.

Reference is now made to FIG. 3, relating to a modification. In thismodification, the coil support or yoke comprises an external annularhousing 121 whose opening is turned towards the internal side of themachine (opposed to that of the electric motor) and which receives thedeclutching coil 122; the second internal annular housing 123 has itsorifice turned towards the external side of the machine; it receives thebraking coil 124. In the coil support 120 are also provided bores 125 inwhich are housed springs 126 resting on the one hand on a cheek 127ofthe case of the machine. The coil 122 is opposite a ring 128 made ofmagnetic material fixed by screws 129 on the cover 94.

The functioning of this modification is identical to that of theembodiment previously described as regards obtaining the various speedsof the machine in the conditions of the high speeds and also that of thelow speed. However, during operation the coil 122 is fed permanently, sothat the magnetic actions developed by said coil apply the coil support120 against the ring of magnetic material 128 as shown in FIG. 3,against the action of the springs 126. When the sleeve 82 is notactuated by the swivel joint 84, i.e. for the high position of thepedal, the springs 96, exerting their action on the cap 92, keep thesliding assembly 54 in the right-hand end position, i.e. for which thepacking 65 cooperates with the wheel 27; this is the low speed of themachine. When the sleeve 82 is actuated by means of the lever 85 in thedirection of the arrow marked in the FIG., i.e. from right to left, thenit is the packing 64 of the plate 61 which cooperates with the face 101of the inertia flywheel 32 and one obtains the various high speeds inaccordance with the degree of driving-in of the pedal, the maximum highspeed being obtained when the plate 61 rotates at the speed of theflywheel 32. Both for the high speeds and for the low speed, the contactbetween the plate 68 of the sliding and rotating assembly 54 and thecoil support 120 is not established.

For the braking, which is caused solely when the machine is in the lowspeed condition, i.e. as shown in FIG. 3, the feeding current of thecoil 122 is interrupted. The magnetic action which was exerted by thecoil 122 disappearing, the springs 126 urge the coil support 120 fromright to left into abutment of the external front face 129 of the coilsupport against the bearing face 130 of the cheek 131. In the course ofthis movement, the support 120 has, by its shoulder 132, brought aboutthe driving in the same direction, by cooperation with the plate 68, ofthe sliding and rotating assembly 54, which draws the packing 65 awayfrom the wheel 27; the limitation of the movement gives the assurancethat the packing 64 remains at a distance from the inertia flywheel 32;the sliding and rotating assembly 54 is therefore disconnected from themotor. For the braking also, the feed of the coil 124 is established andthe magnetic action which it develops applies the fixed support 120under pressure against the plate 68, with interposition of the frictionpacking 102, so that one effects the braking in the same conditions asfor the embodiment previously described.

In this modification, a current breakdown, by interrupting the feed ofthe coil 122, automatically brings the machine into its declutchedcondition. The result is, if the machine is in the course of working, amore rapid stoppage of the latter, the in ertia of the flywheel and ofthe electric motor then being without any influence.

In this modification, likewise, if a current breakdown occurs when, themachine being at a standstill, one is effecting some maneuver on thislatter which obliges the operator to put his fingers into contact with apart of the machine, the machine stays at a standstill, even if themotor is rotating at the moment of the breakdown, so that this latterhas no annoying consequence.

Reference is now made to FIGS. 4 and 5, relating to a device for theautomatic performance of an operation process of a machine, moreespecially a sewing machine provided with the driving device asdescribed.

This device comprises a rotor 200 and a stator 201. The rotor 200 iskeyed on a shaft actuated by the general movement of the machine, forexample the main shaft 202 of the sewing machine. To this end, the rotorcomprises a dish 203 slipped on said shaft, secured to the shaft byscrews 204 traversing the dish. The dish 203 is followed by a tubularextension 205, which serves for revolubly mounting the rotor on thestator by means of a ball bearing 206. The stator 291 has the generalshape of an annular disc 207, with an internal rim 208, integral withthe fixed cage of the ball bearing 206, and an external rim 209, onwhich is placed a protective cap 210. The stator 201 is extended by atail 223, which passes between the resilient branches 224 and 225 of aclip, thus enabling to angularly adjust the position of the stator aboutthe axis of rotation 226 of shaft 202.

The rotor 202 also comprises a hub 211, integral with the dish 203 by ascrewing of the tail 212 of the hub in the tubular projection 205. Thehub has a rim 213, presenting two parallel elongated housings 214 and215, diametrically opposed and perpendicular to their common diameter,one of which receives a magnetized rectilinear bar 216 and the other oneof which receives a bar 217, not magnetized, but balancing the bar 216.

On the stator disc 207, fixed on the edge of the internal rim 208, isplaced a first switch support 218 and a second switch support 219, saidsupports being mounted so as to be able to be angularly adjusted onewith regard to the other, by means of a circular slide 220 andimmobilized by screws 221 and 222. The support 218 and the support 219carry magnetosensitive electrical switches, 227 and 228 respectively, ata distance from the axis 226 which is substantially that of the bars 216and 217.

The magnetosensitive switches 227 and 228 are advantageously flexibleblade switches of a known type, respectively lLS,, 1LS (HO. 6), thecontacts of which are shown respectively at 229230 and 231-232, saidcontacts cooperating with one another when the switch is placed in amagnetic field and being on the contrary separated from one another bythe elasticity effect of the blades, respectively 233- -234 and 235-236,in the absence of a magnetic field. An electric control source 237 hasits negative pole 258 earthed and its other pole 239 is connected by aconductor 240, on which there is a switch 1,, to the input A of acircuit 242. The switch l is, for example, controlled from the lever 85,so as to be closed only when the lever is in the position shown in FIG.1, i.e. when the operator is not pressing on the pedal, and is open foras long as the pedal is depressed, even slightly.

On the conductor 243 of the circuit 242 connected to the input A isprovided a switch 1 which, according to its position, puts the conductor243 into electrical relation with a first conductor 244 or a secondconductor 245. The conductor 244 is connected to an input 246 of theswitch lLS,, whose output 247 is connected, by a conductor 248, to theoutput D of the circuit 242. A branch 249 of the conductor 244 isconnected to a second output B of the circuit 242, connected to theanode 250 of a controlled diode T, the gate 251 of which is connected tothe common point 252 of two resistances R and R interposed between theoutput D and earth. A condenser C has its plate 253 connected to thepoint 252 and its other plate 254 connected to earth. The cathode 255 ofthe controlled diode T is connected to the winding 256 ofa relay RY,whose armature 257, when the relay is excited, cooperates with a contact258 to close a feed circuit of the winding controlling the braking,which is the winding 76 in the first embodiment and the winding 124 inthe second.

The mounting of the second blade switch [LS is similar to that of thefirst, but a switch I, is inserted between the terminal 259 of saidswitch and the conductor 245. The moving member 260 of switch I,cooperates with the contacts 261 and 262, to effect the feed of theswitch lLS only when the relay RY is not fed. The terminal 259 isconnected to the output B by a branch 263 which comprises a diode D Anautofeed circuit 264 is inserted between the conductor 243 and theterminal 259 and comprises a switch 1 having a moving member 265 andfixed contacts 266 and 267.

The operation is as follows:

For as long as the pedal is depressed, the machine is at its conditionof high speed, its speed being at the maximum that for which the pulleyrotates at the speed of the inertia flywheel 32, and being able to adoptlower values if, as a function of the pressure exerted on the pedal, theapplication force of the packing 64 against the inertia flywheel permitsslip between the two members. For as long as the pedal is not returnedto its high position, by means of resilient means which are not shown,the switch'l is open, so that the controlling device ofthe brakingcannot be fed. When the pedal is in its top position, the switch I isclosed, so that the controlling device of the braking can be fed by thesource 237.

The device according to the invention is such that, in the course of thedecreasing speed of the machine from a high speed, the braking iseffectively actuated only when the speed of the machine reaches, whendecreasing, a predetermined value, which is advantageously that of thelow speed, i.e. that at which the machine rotates when the clutchbetween the packing 65 and the wheel 67 is effective.

The diagram of FIG. 7 shows the values of the potential at the output Das a function of the time for high speeds of the machine, the width ofthe rectangular pulses 268 being comparatively very slight.

The diagram of FIG. 8 is representative of the value of the potential ofthe gate 251, which is that of the plate 253 of the condenser C. Themaximum value 269 of said potential is lower than the triggering tensionof the controlled diode T, shown by the line U of the diagram.

As the machine slows down, the width of the rectangular pulses 268increases and the maximum value of the potential of the gate 251increases, as shown by the diagrams of FIGS. 9 and 10. When this maximumvalue reaches the value U the diode T suddenly becomes conductive. Thepotential of the gate 251 then varies as shown in FIG. 11.

Upon the triggering of the controlled diode T, the relay RY, which wasnot traversed by any current, becomes fed by connection of its winding256 to the source 237, by means of a circuit which comprises: thecontrolled diode T, the conductor 270 as far as the output B, theconductor 249, the conductor 244, the switch 1 the conductor 243, theswitch 1,, as far as the pole 239 of the source 237. The pedal not beingsunk in, the machine is disconnected from the electric motor; therotating mass has a very determined inertia. The triggering of diode Tis obtained when the magnetized bar 216 passes in front of the switch1LS,, therefore for a well determined angular position of the rotor,i.e. of the rotating assembly which then has exactly the predeterminedangular speed. The kinetic energy of the rotating mass thus has apredetermined value so that, by application of the determined brakingforce resulting from the excitation of the winding 76 or of the winding124, one ends up with the stoppage for a constant angular position ofthe machine, which can be a predetermined position for the needle of thesewing machine, for example the bottom position or the top position. Aninitial adjustment can be obtained by angular shifting of the statorabout the axis 226.

When the moving member 271 of the switch l cooperates with the contact272, it is the switch ILS which is operative and the stoppage takesplace, for example for the bottom position of the needle, by the processwhich has been defined above.

When, on the other hand, the moving member 271 cooperates with the otherfixed contact 273, the switch 1LS,, is inoperative and, on the otherhand, it is the switch lLS which becomes operative. The stoppage takesplace in the angular position determined by the location of said switch1LS The angular shifting of the first position of stoppage and of thesecond position of stoppage can be modified initially at will, bydisplacing the first stator support 218 with regard to the secondsupport 219.

The passage of the moving member 271 from its position of cooperationwith the contact 272 to its position of cooperation with the contact 273can take place by pressing on a special button on the machine. There isprovided for example that, without any load, it is the contact 272 whichis operative,

so that upon the braking the machine stops with its needle in the lowerposition. If, simultaneously with letting go of the pedal, the operatorpresses the button making the contact 273 operative, then, upon thebraking, the machine stops with its needle in the upper position.

One can also obtain the storage of the machine with its needle in thebottom position, then, by a subsequent action, make it pass to the upperposition.

We claim:

1. A driving and stopping device of a machine, particularly a sewingmachine comprising, between an electric driving motor and an outputpulley or the like connected to the machine, a speed reducing train andan electromagnetic clutch and brake device having a longitudinallysliding support, two coaxial coils means in said support, a slidinglymovable assembly integral with the coupling member of said clutch deviceand adapted to be slidingly displaced upon excitation of one said coilmeans, and a friction packing, housed in said support, adapted to beapplied against a plate integral with said assembly upon excitation ofsaid other coil means for the braking of the machine.

2. A device as claimed in claim I, wherein the excitation of theelectromagnetic device results in the attraction of the coil meanssupport by a fixed check of the housing of the device, the limitation ofthe sliding movement of said support being obtained by abutment of thesame against said cheek.

3. A device as claimed in claim 2, further comprising elastic meansurging said support away from said cheek and stop means comprisingscrews housed in a cover of the housing for limiting the action of saidelastic means.

4. A device as claimed in claim 2, further comprising spring meanshoused in the device housing urging said sliding assembly towards itsposition in which the coupling member cooperates with the output wheelof the speed reducing train, for the drive at low speed.

5. A device as claimed in claim 4, further comprising, for the drive athigh speed, a control lever, connected to a pedal or the like, todisplace the sliding assembly against the action of said spring means.

6. A device as claimed in claim 1, further comprising means supplying acurrent pulse at each revolution of a member forming a part of themachine, said pulse having a width all the greater as said member turnsmore slowly and electronic threshold means controlled by said pulse forinitiating the braking action in view of stopping the machine in apredetermined position.

7. A device as claimed in claim 6, wherein said rotating member is adisc integral with the main shaft of the machine, said disc carrying amagnetized bar which cooperates with a flexible blades switch to supplysaid current pulse.

8. A device as claimed in claim 7, wherein said switch is carried by astator of adjustable position about the axis of the shaft ofthe machine.

9. A device as claimed in claim 7, wherein said stator carries severalswitches having flexible blades separately operative in view ofcontrolling the stoppage of the machine in one of several predeterminedpositions.

